Merge pull request #67 from pythonbpf/32int_support

add i32 support and special support for xdp_md with zext

Author: varun-r-mallya

pythonbpf/allocation_pass.py

@@ -1,6 +1,6 @@
 import ast
 import logging
-
+import ctypes
 from llvmlite import ir
 from .local_symbol import LocalSymbol
 from pythonbpf.helper import HelperHandlerRegistry
@@ -81,7 +81,7 @@ def _allocate_for_call(builder, var_name, rval, local_sym_tab, structs_sym_tab):
         call_type = rval.func.id
 
         # C type constructors
-        if call_type in ("c_int32", "c_int64", "c_uint32", "c_uint64"):
+        if call_type in ("c_int32", "c_int64", "c_uint32", "c_uint64", "c_void_p"):
             ir_type = ctypes_to_ir(call_type)
             var = builder.alloca(ir_type, name=var_name)
             var.align = ir_type.width // 8
@@ -249,7 +249,58 @@ def _allocate_for_attribute(builder, var_name, rval, local_sym_tab, structs_sym_
             ].var = base_ptr  # This is repurposing of var to store the pointer of the base type
             local_sym_tab[struct_var].ir_type = field_ir
 
-            actual_ir_type = ir.IntType(64)
+            # Determine the actual IR type based on the field's type
+            actual_ir_type = None
+
+            # Check if it's a ctypes primitive
+            if field.type.__module__ == ctypes.__name__:
+                try:
+                    field_size_bytes = ctypes.sizeof(field.type)
+                    field_size_bits = field_size_bytes * 8
+
+                    if field_size_bits in [8, 16, 32, 64]:
+                        # Special case: struct_xdp_md i32 fields should allocate as i64
+                        # because load_ctx_field will zero-extend them to i64
+                        if (
+                            vmlinux_struct_name == "struct_xdp_md"
+                            and field_size_bits == 32
+                        ):
+                            actual_ir_type = ir.IntType(64)
+                            logger.info(
+                                f"Allocating {var_name} as i64 for i32 field from struct_xdp_md.{field_name} "
+                                "(will be zero-extended during load)"
+                            )
+                        else:
+                            actual_ir_type = ir.IntType(field_size_bits)
+                    else:
+                        logger.warning(
+                            f"Unusual field size {field_size_bits} bits for {field_name}"
+                        )
+                        actual_ir_type = ir.IntType(64)
+                except Exception as e:
+                    logger.warning(
+                        f"Could not determine size for ctypes field {field_name}: {e}"
+                    )
+                    actual_ir_type = ir.IntType(64)
+
+            # Check if it's a nested vmlinux struct or complex type
+            elif field.type.__module__ == "vmlinux":
+                # For pointers to structs, use pointer type (64-bit)
+                if field.ctype_complex_type is not None and issubclass(
+                    field.ctype_complex_type, ctypes._Pointer
+                ):
+                    actual_ir_type = ir.IntType(64)  # Pointer is always 64-bit
+                # For embedded structs, this is more complex - might need different handling
+                else:
+                    logger.warning(
+                        f"Field {field_name} is a nested vmlinux struct, using i64 for now"
+                    )
+                    actual_ir_type = ir.IntType(64)
+            else:
+                logger.warning(
+                    f"Unknown field type module {field.type.__module__} for {field_name}"
+                )
+                actual_ir_type = ir.IntType(64)
 
             # Allocate with the actual IR type, not the GlobalVariable
             var = _allocate_with_type(builder, var_name, actual_ir_type)

pythonbpf/assign_pass.py

@@ -152,15 +152,30 @@ def handle_variable_assignment(
     if val_type != var_type:
         if isinstance(val_type, Field):
             logger.info("Handling assignment to struct field")
+            # Special handling for struct_xdp_md i32 fields that are zero-extended to i64
+            # The load_ctx_field already extended them, so val is i64 but val_type.type shows c_uint
+            if (
+                hasattr(val_type, "type")
+                and val_type.type.__name__ == "c_uint"
+                and isinstance(var_type, ir.IntType)
+                and var_type.width == 64
+            ):
+                # This is the struct_xdp_md case - value is already i64
+                builder.store(val, var_ptr)
+                logger.info(
+                    f"Assigned zero-extended struct_xdp_md i32 field to {var_name} (i64)"
+                )
+                return True
             # TODO: handling only ctype struct fields for now. Handle other stuff too later.
-            if var_type == ctypes_to_ir(val_type.type.__name__):
+            elif var_type == ctypes_to_ir(val_type.type.__name__):
                 builder.store(val, var_ptr)
                 logger.info(f"Assigned ctype struct field to {var_name}")
                 return True
-            logger.error(
-                f"Failed to assign ctype struct field to {var_name}: {val_type} != {var_type}"
-            )
-            return False
+            else:
+                logger.error(
+                    f"Failed to assign ctype struct field to {var_name}: {val_type} != {var_type}"
+                )
+                return False
         elif isinstance(val_type, ir.IntType) and isinstance(var_type, ir.IntType):
             # Allow implicit int widening
             if val_type.width < var_type.width:

pythonbpf/expr/expr_pass.py

@@ -12,6 +12,7 @@
     get_base_type_and_depth,
     deref_to_depth,
 )
+from pythonbpf.vmlinux_parser.assignment_info import Field
 from .vmlinux_registry import VmlinuxHandlerRegistry
 
 logger: Logger = logging.getLogger(__name__)
@@ -279,16 +280,45 @@ def _handle_ctypes_call(
     call_type = expr.func.id
     expected_type = ctypes_to_ir(call_type)
 
-    if val[1] != expected_type:
+    # Extract the actual IR value and type
+    # val could be (value, ir_type) or (value, Field)
+    value, val_type = val
+
+    # If val_type is a Field object (from vmlinux struct), get the actual IR type of the value
+    if isinstance(val_type, Field):
+        # The value is already the correct IR value (potentially zero-extended)
+        # Get the IR type from the value itself
+        actual_ir_type = value.type
+        logger.info(
+            f"Converting vmlinux field {val_type.name} (IR type: {actual_ir_type}) to {call_type}"
+        )
+    else:
+        actual_ir_type = val_type
+
+    if actual_ir_type != expected_type:
         # NOTE: We are only considering casting to and from int types for now
-        if isinstance(val[1], ir.IntType) and isinstance(expected_type, ir.IntType):
-            if val[1].width < expected_type.width:
-                val = (builder.sext(val[0], expected_type), expected_type)
+        if isinstance(actual_ir_type, ir.IntType) and isinstance(
+            expected_type, ir.IntType
+        ):
+            if actual_ir_type.width < expected_type.width:
+                value = builder.sext(value, expected_type)
+                logger.info(
+                    f"Sign-extended from i{actual_ir_type.width} to i{expected_type.width}"
+                )
+            elif actual_ir_type.width > expected_type.width:
+                value = builder.trunc(value, expected_type)
+                logger.info(
+                    f"Truncated from i{actual_ir_type.width} to i{expected_type.width}"
+                )
             else:
-                val = (builder.trunc(val[0], expected_type), expected_type)
+                # Same width, just use as-is (e.g., both i64)
+                pass
         else:
-            raise ValueError(f"Type mismatch: expected {expected_type}, got {val[1]}")
-    return val
+            raise ValueError(
+                f"Type mismatch: expected {expected_type}, got {actual_ir_type} (original type: {val_type})"
+            )
+
+    return value, expected_type
 
 
 def _handle_compare(

pythonbpf/functions/function_debug_info.py

@@ -49,17 +49,27 @@ def generate_function_debug_info(
                 "The first argument should always be a pointer to a struct or a void pointer"
             )
         context_debug_info = VmlinuxHandlerRegistry.get_struct_debug_info(annotation.id)
+
+        # Create pointer to context this must be created fresh for each function
+        # to avoid circular reference issues when the same struct is used in multiple functions
         pointer_to_context_debug_info = generator.create_pointer_type(
             context_debug_info, 64
         )
+
+        # Create subroutine type - also fresh for each function
         subroutine_type = generator.create_subroutine_type(
             return_type, pointer_to_context_debug_info
         )
+
+        # Create local variable - fresh for each function with unique name
         context_local_variable = generator.create_local_variable_debug_info(
             leading_argument_name, 1, pointer_to_context_debug_info
         )
+
         retained_nodes = [context_local_variable]
-        print("function name", func_node.name)
+        logger.info(f"Generating debug info for function {func_node.name}")
+
+        # Create subprogram with is_distinct=True to ensure each function gets unique debug info
         subprogram_debug_info = generator.create_subprogram(
             func_node.name, subroutine_type, retained_nodes
         )

pythonbpf/type_deducer.py

@@ -16,6 +16,8 @@
     "c_long": ir.IntType(64),
     "c_ulong": ir.IntType(64),
     "c_longlong": ir.IntType(64),
+    "c_uint": ir.IntType(32),
+    "c_int": ir.IntType(32),
     # Not so sure about this one
     "str": ir.PointerType(ir.IntType(8)),
 }

pythonbpf/vmlinux_parser/vmlinux_exports_handler.py

@@ -1,6 +1,6 @@
 import logging
 from typing import Any
-
+import ctypes
 from llvmlite import ir
 
 from pythonbpf.local_symbol import LocalSymbol
@@ -94,32 +94,30 @@ def handle_vmlinux_struct_field(
                 f"Attempting to access field {field_name} of possible vmlinux struct {struct_var_name}"
             )
             python_type: type = var_info.metadata
-            globvar_ir, field_data = self.get_field_type(
-                python_type.__name__, field_name
-            )
+            struct_name = python_type.__name__
+            globvar_ir, field_data = self.get_field_type(struct_name, field_name)
             builder.function.args[0].type = ir.PointerType(ir.IntType(8))
-            print(builder.function.args[0])
             field_ptr = self.load_ctx_field(
-                builder, builder.function.args[0], globvar_ir
+                builder, builder.function.args[0], globvar_ir, field_data, struct_name
             )
-            print(field_ptr)
             # Return pointer to field and field type
             return field_ptr, field_data
         else:
             raise RuntimeError("Variable accessed not found in symbol table")
 
     @staticmethod
-    def load_ctx_field(builder, ctx_arg, offset_global):
+    def load_ctx_field(builder, ctx_arg, offset_global, field_data, struct_name=None):
         """
         Generate LLVM IR to load a field from BPF context using offset.
 
         Args:
             builder: llvmlite IRBuilder instance
             ctx_arg: The context pointer argument (ptr/i8*)
             offset_global: Global variable containing the field offset (i64)
-
+            field_data: contains data about the field
+            struct_name: Name of the struct being accessed (optional)
         Returns:
-            The loaded value (i64 register)
+            The loaded value (i64 register or appropriately sized)
         """
 
         # Load the offset value
@@ -164,13 +162,61 @@ def load_ctx_field(builder, ctx_arg, offset_global):
             passthrough_fn, [ir.Constant(ir.IntType(32), 0), field_ptr], tail=True
         )
 
-        # Bitcast to i64* (assuming field is 64-bit, adjust if needed)
-        i64_ptr_type = ir.PointerType(ir.IntType(64))
-        typed_ptr = builder.bitcast(verified_ptr, i64_ptr_type)
+        # Determine the appropriate IR type based on field information
+        int_width = 64  # Default to 64-bit
+        needs_zext = False  # Track if we need zero-extension for xdp_md
+
+        if field_data is not None:
+            # Try to determine the size from field metadata
+            if field_data.type.__module__ == ctypes.__name__:
+                try:
+                    field_size_bytes = ctypes.sizeof(field_data.type)
+                    field_size_bits = field_size_bytes * 8
+
+                    if field_size_bits in [8, 16, 32, 64]:
+                        int_width = field_size_bits
+                        logger.info(f"Determined field size: {int_width} bits")
+
+                        # Special handling for struct_xdp_md i32 fields
+                        # Load as i32 but extend to i64 before storing
+                        if struct_name == "struct_xdp_md" and int_width == 32:
+                            needs_zext = True
+                            logger.info(
+                                "struct_xdp_md i32 field detected, will zero-extend to i64"
+                            )
+                    else:
+                        logger.warning(
+                            f"Unusual field size {field_size_bits} bits, using default 64"
+                        )
+                except Exception as e:
+                    logger.warning(
+                        f"Could not determine field size: {e}, using default 64"
+                    )
+
+            elif field_data.type.__module__ == "vmlinux":
+                # For pointers to structs or complex vmlinux types
+                if field_data.ctype_complex_type is not None and issubclass(
+                    field_data.ctype_complex_type, ctypes._Pointer
+                ):
+                    int_width = 64  # Pointers are always 64-bit
+                    logger.info("Field is a pointer type, using 64 bits")
+                # TODO: Add handling for other complex types (arrays, embedded structs, etc.)
+                else:
+                    logger.warning("Complex vmlinux field type, using default 64 bits")
+
+        # Bitcast to appropriate pointer type based on determined width
+        ptr_type = ir.PointerType(ir.IntType(int_width))
+
+        typed_ptr = builder.bitcast(verified_ptr, ptr_type)
 
         # Load and return the value
         value = builder.load(typed_ptr)
 
+        # Zero-extend i32 to i64 for struct_xdp_md fields
+        if needs_zext:
+            value = builder.zext(value, ir.IntType(64))
+            logger.info("Zero-extended i32 value to i64 for struct_xdp_md field")
+
         return value
 
     def has_field(self, struct_name, field_name):

tests/c-form/Makefile

@@ -1,19 +1,23 @@
 BPF_CLANG := clang
-CFLAGS := -O0 -emit-llvm -target bpf -c
+CFLAGS := -emit-llvm -target bpf -c
 
 SRC := $(wildcard *.bpf.c)
 LL := $(SRC:.bpf.c=.bpf.ll)
+LL2 := $(SRC:.bpf.c=.bpf.o2.ll)
 OBJ := $(SRC:.bpf.c=.bpf.o)
 
 .PHONY: all clean
 
-all: $(LL) $(OBJ)
+all: $(LL) $(OBJ) $(LL2)
 
 %.bpf.o: %.bpf.c
 	$(BPF_CLANG) -O2 -g -target bpf -c $< -o $@
 
 %.bpf.ll: %.bpf.c
-	$(BPF_CLANG) $(CFLAGS) -g -S $< -o $@
+	$(BPF_CLANG) -O0 $(CFLAGS) -g -S $< -o $@
+
+%.bpf.o2.ll: %.bpf.c
+	$(BPF_CLANG) -O2 $(CFLAGS) -g -S $< -o $@
 
 clean:
-	rm -f $(LL) $(OBJ)
+	rm -f $(LL) $(OBJ) $(LL2)

tests/c-form/i32test.bpf.c

@@ -0,0 +1,15 @@
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+SEC("xdp")
+int print_xdp_data(struct xdp_md *ctx)
+{
+    // 'data' is a pointer to the start of packet data
+    long data = (long)ctx->data;
+
+    bpf_printk("ctx->data = %lld\n", data);
+
+    return XDP_PASS;
+}
+
+char LICENSE[] SEC("license") = "GPL";

tests/failing_tests/vmlinux/args_test.py

@@ -0,0 +1,30 @@
+import logging
+
+from pythonbpf import bpf, section, bpfglobal, compile_to_ir
+from pythonbpf import compile  # noqa: F401
+from vmlinux import TASK_COMM_LEN  # noqa: F401
+from vmlinux import struct_trace_event_raw_sys_enter  # noqa: F401
+from ctypes import c_int64, c_int32, c_void_p  # noqa: F401
+
+
+# from vmlinux import struct_uinput_device
+# from vmlinux import struct_blk_integrity_iter
+
+
+@bpf
+@section("tracepoint/syscalls/sys_enter_execve")
+def hello_world(ctx: struct_trace_event_raw_sys_enter) -> c_int64:
+    b = ctx.args
+    c = b[0]
+    print(f"This is context args field {c}")
+    return c_int64(0)
+
+
+@bpf
+@bpfglobal
+def LICENSE() -> str:
+    return "GPL"
+
+
+compile_to_ir("args_test.py", "args_test.ll", loglevel=logging.INFO)
+compile()